The present invention relates to color video systems and in particular to color video systems in which sequentially filtered signals are asynchronously generated and subsequently framed.
In color video it is typical to separate colors in a field of view through a color wheel having plural color filters spun in the field of view of a video camera. The wheel spins synchronously at a rate slow enough to permit a full frame of video to be generated by the camera for each color in the wheel. The synchronous wheel motion permits the video stream from the camera to be identified by time of occurrence with the color of the filter in the field of view.
The requirement for synchronous driving of the color wheel means that the system cannot properly separate colors in cases where there is disturbance to synchronization, and further involves the use of expensive synchronous motors and synchronous excitation run at an appropriate frequency.
In other applications it is desirable to be able to position one of several filter characteristics in the field of view of a video camera to accommodate different transmissivity needs in scenes of greatly varying luminosity as is found in applications to rocket photography, or to respond to different polarization characteristics of incident light or other radiation without the need for complex synchronous spin systems.